Sprocket fastening means



Oct. 21, 1952 H. F. HEIDEGGER ET AL 2, 14

SPROCKET FASTENING MEANS Filed March 8, 1949 ATTORNEY drill bored.

Patented Oct. 21, 1952 Y STATES ENT'OFFICEW Henry F. Heidegger, Glen Ridge, N. J andWilly Borberg, Astoria, N. Y., assignors to Interna- 'tional Projector Corporation, Bloomfield, N. J

a corporation of Delaware i Application March B, 1949, Serial No. 80,226

Thisinvention' relates to improvements in sprocket fastening means, and is more particularly directedto' a novel means to removably att'ach a rotatable driving element, such asa film feeding sprocket, pulley, gear or other rotatable element,-.to its shaft. l l Though the invention is capable of use in mounting a great variety of sprockets, pulleys, h'ubbed gears or similar elements to rotary shafts, it is especiallyfiapplicable for use in'mounting film-engaging sprockets on projector shafts. In motion picture projecting machines, it is highly important that the continuous film be led to the projection aperture and drawn from in front of such aperture smoothly, evenly and swiftly and without undulations or lateral play. To attain these ends, thefilm web travels from the upper reel over or under successive, continuously running and intermittently rotating toothed sprockets the teeth of which enter sprocket holes formed in the margin of the film'web. The film is held engaged with the teeth bysu'itably'supported grooved guide or pad rollers embracing theycircular series of teeth formed on the enlarged rims 'or'fiangesofthe sprockets. Aclearance is allowed-between the pad rollers and the peripheries of the end flanges of thetoothed sprockets to avoid pinching thefilm. 'To increase the 1 rate .ofmanufacture of the sprockets used in motion picture projecting machines, resortis often made to forming the axially extending bores of the sprockets bybroaching and reaming. "Any, .bore that is broachedbecomes slightly barrel-shaped because such operation pushesthemetal aside or compacts the metal instead of cleanly removing it, as isthe case when is removed and the operation isvcompletedjthe metal tends slightly to return to its former position. -Barrel-shaped' bores after broaching and reamingare-not readily detected by the usual guages since the opposite ends ofthe bores are generally of the correct diameter; a When such a sprocket is mounted on a rotatable shaft, it

tends to have an'elliptical orbit or to wobble Also, after the broachingpressure securing the sprockets 8 Claims. (01. ear-52.08)

film sprockets to their shafts. For instance; :it has been'customary to attach the sprocket wheels" to their-shafts by ordinary set screws threaded into holes extending radially through the sprocket barrels fromthe peripheries thereof into the bores and with the inner ends of the set screws bearing firmly against the shafts. One great objection to the customary method of attaching the sprocket wheelsto their shafts by ordinary set screws is-that when the retaining set screw is turned down tightly on the shaft, ittends to bend the shaft when the bores of the sprockets are barrel-shaped or otherwise out of true alignment. Also, as the bores of the sprocketseven when accurate are slightly larger in diameter than the diameter of the shafts, this method of fastening takes up all the clearance on one side of the sprocket bore and doubles the clearance on'the diametrically opposite side of the sprocket bore, resulting in eccentrically positioning the sprocket on theshaft. Similar results occur if a reverse arrangementof rigidly to their shafts is resorted to, wherein the radial hole in the sprocket is unthreaded, but is shouldered or counter-bored, and a threaded hole formed radially in the shaft. In this form, radial holes in the sprocket and shaft are aligned and a headed set screw entered in the unthreaded,counter-bored radial sprocket hole and screwed into the threaded hole in the shaft.- When the set screw is tightened with its head against the counter-bored shoulder in the radial sprocket hole, the shaft is drawn towards the screw instead of being forcedaway, as in the first example, but theeccentric positioning of the sprocket on the shaft occurs just as above explained because the clearance is taken up be tween the sprocket bore and the shaft.

Another objection present in the set screw methodof securing pulleys, sprockets and the like fixedly to "shafts is that when setting the screw fast on the shaft, theforce required to firm-- lyengagethe screw with the shaft not only causes theend of the screw toindent the shaft, but as the screwisgiven the last turn or turns, the end of the screw raises a bur on the shaft which forms an obstruction preventing the attached sprocket or the like from being readily-shot on 'oroffoftheshaft; U One principal object of the present invention is to provide means to attach a sprocket, pulley, gear or similar element to a shaft by novel'means which avoids the foregoing disadvantages while retaining the advantages of easy application and removal of the sprocket. l l V It is thus an object of the present invention to provide means to secure the sprocket or analogous part on its shaft against relative rotation and in such manner as to avoid not only any likelihood of eccentrically shifting the sprocket, but also to avoid any danger of bending the shaft or the misalignment .ofv the" sprocket thereon-as heretofore encountered. The invention further contemplates mounting the sprocket somewhat loosely on its shaft instead of fastening it tightly thereto, and the provision of means which not onlyserves as a key to transmit rotary motion to the sprocket but also retains the sprocket on the shaft and aligned "in proper balance therewith.

Other objects and advantages will be more fully set forth hereinafter and particularly pointed out in the claims.

In the accompanyin drawings,

Fig. 1 is a view partly in section of the sprocket andvshaft embodying the invention together with a-fragmentaryI portion --of the: projector frame;

Fig; 2 is navertical view-partly in section of -a modification of- -theform shown in- Fig. 1;

Fig;- 3 is a detal view of-"a fastening nut having-a concave contact face; as used-in the present invention. 7 I

"The present invention eliminates the; foregoing: and other-disadvantages (by avoiding the necessity for firmly-clamping'the sprocket fricti'onally- :orotherwise to the shaft, and instead of fixedly-securin the-".-spr.ocket-and -shaft together as a substantially integral unit, the sprocket :ismounted onthe shaft "without distortion-of the'shafa 'to-enable the sprocket to correctly.positioned=ontheirshafts-to maintain .r

a proper-talignment ofi the film-as it is fed from one sprocket to another at an approximate-rate of ninety feet -per -'minute i-ncommercial machines during 1 projection.

Asaaanovel means to attachthe*:sprocket=;to

the shaft in- 'suchsmanner .as to prevent material longitudinal movement of the: spro kct on' its shaft, an unthreaded holeuor'passage I S-isdrilled diametrically through the barrel-cf the sprocket 4.3, such :hole intersecting the 'bore IZ'ofthe sprocket at right angles. :Theshaft: II-is also provided with an iunthreaded hole-tor :locking shaft 'bore 2 I I drilled 1 diametrically therethrough and of less=diametenthan :the I diamet-rical.v passage I5 formed: through the sprocket.

I '-".I'he sprocket {I2 is -slid'onto the free end: of

the shaft H and the passage I 5 of "the sprocket is aligned with the locki-ng shaft. bore- 2 I--in the shaft, after which a cylindrical thimble or collar I 9- 'of:' 1 an outside diameter: substantially fitting chef-passage =I.5,- ;-isentered into-*oneend or 'saidsprocket passage and slid along; the pas,- sage until its inner; concave end-abutsyandi conforms to :the 'peripheryrof the drive shaft- 1 .I ihe thimble or collar is axially bored-easat to substantially the same diameter as the dia metrically extending locking shaft bore 2I in the shaft II and the outer end of the thimble may, if desired, be counter-bored to form an annular shoulder I18. When the larger sprocket passage I5 is aligned with the locking shaft bore 2| in the drive shaft, the bore 20 of-the thimble I9 lies in alignment with the bore 2| extending through the drive shaft. A headed screw .IB is then entered in that end of the sprocket passage I5 containing the thimble or collar I9, the screw passing through the bore 20 of the thimble 19 until the head I6 of the screw seats in they counter-bored outer end of the thimble against the shoulder I8. The screw is of a length sufficient to pass through the transverse docking bore 2| in the shaft, with its threaded end 24 projecting into the opposite aligned section of the sprocket passage I5. The diameter of the screw I0 is such as to slidingly fit the bore 2|],ofthe-thimble I9 and the-bore 2| drilled transversely of the shaft 11. Preferablywa tapered or-a frusto-conical threaded nut 22" is employed -to engage thescrew 40. This nut-is formed-with a concave contact face as shown in section in Fig. 3, to fit the peripheryliofathe shaft-to -avoid' flattening the-rshaft. 'Ihe'idiameter of 'the -inner end of the nut substantially fits that section of the sprocket passage ':l5 i'n'to which the threaded'end" 24"1'of 'the headed screw In projects. *Kerfs' IT and 23, -formed"iin'the head-16' of the screw and-in the outer smaller endof the: frusto coni'cal nut 22 respectively, facilitate turning the nut =down on the threaded end of the screw with the nut-preferably being held against 'rotatiom until: the larger end for concave base-of the nut :is' drawn :into conta'ct with the' arcuate or rounded periphery ofu the shaft. Thecollar'IB may :be likewise formed with aconcave f inner endnto 'fit the shattl in corresp'ondence w'i-th the inner-endof thetfrustoc0nical-nut'22. i

The collar =or thimblei ler-preventsvithe shaft I I from being marred-wvhen' the screw"I0 is tightened. v If 'no collar were: present;the inner face ofthe screw 1 head' rlfipxwhenlit" contacted the shaft and 'wasthereafter turnedP-toI Lti'ghten its holding effect would dent therpolished periphery "of the shaft, and set up? a 'hur' preventing the ready-removal of: theiisprocket from the shaft rwhen desired. I The 'provision of the collar eliminates this possibility. Since the 'tapered nut-221s not-seated irr a' collarfit is desirable that-the key 'be tightened by "turning the screw instead of -the'nut; the kern 23 fin'l-the nut enabling the insertion *ofaxa tool-J therein to hold f the nut: stationary? as -the s'crewiis turned down.

--*It *will be noted 1 'thatfitheiiscrew :I 0 of less length than the :length of the' sprocketiipassage I 5 ato-aavoidthe possibility of lnterference with the filmextending") between the sprocket too-thed .rims- ,at- :the opposite 'ends ofxthei sprocket. ther; the headed's s'cre'w Ill "awith its? thirnblei SIB andinut 22 constitute a keynto tr'an'sm'it the ro'tationzof the drive shaft I we theisprocket' -I 31mins leaving the sprocket =free and-'inp'ropepalignment and balance 'relativeto the shaft. The 'screw l0 wim -itsthim-ble :or rcoll'ar =I9': ana mia-:22: prevents endwise or'axialimovement. iof thej'sprocket on {the shaftwas the collarrfits snugly .-in"-:1the pas sage- I 5- to. hold the sprocket-wheref-adjustecl on the shaft. The: screw 'withi its attach'd p'arts constitutes a substantially integral;sthoughi're movableppart :ofthe shaft and; cont'act'lof ithe col-larand the nut against diametricallyiopposed surfaces of the-shaft equalizes the: prefssureton both sidesof theshaft tothusavoid any bendin'g'oftheshaft. 11151 The form shown in Fig; 2 is substantially like that shown in Figs- 1, but, in addition; shows i a circular cupped spring-washer 25 interposed be tween" the inner end of the thimble l9 and the periphery of the drive shaft I I. fThe purpose of-the washer is to take up axial pla y of the sprocketl3with'regard to its shaft. Ifhe-screw l passes through a hole centrallybf the"cupped spring washer' sothat when the nut #22 is 1 drawn snugly against the shaft, thecupped "spring is slightlyfiattened-by contact with the inner face of *the thimble l9x to "spread its circumferential edge toen'gage the-periphery of thebore I'E'ahd take up an i p ay between the washer *andthe litr l: The "flattening or spreading of-the cupped *washer causes its centrai-aperture to grip the threaded shank of the screw 10 to rare as any clearance there present, and: it will bfe noted that there is "no unbalanced 1 radial pressure :brought to bearon the shaft such-as would tend-to bend th'eshaft. The spring-washer-also tends to conform to the curvature 'of thefshafti Changes and alterations '"may be =niade in the forms and arrangements of" the several'parts described without departing from the spirit and scope of theinventioni i I i What is'claimed is:

1. The combination with a rotary shaft, and an element havin an axial bore to accommodate the shaft for rotation thereby; of means to key said element to the shaft in suchmanner as to relieve the shaft of,unbalanced radial stress and retain the element on the shaft, comprising a headed and threaded fastening means; said; elemerit having an unthreaded passage of substantially uniform diameter formed diametrically therethrough to intersect the axial borej' said shaft having a hole diametrically therethrough of less diameter than the passage and with which the passage through the element is aligned a portion of the fastening means extending within the unthreaded passage in said element and the alignedhole through the shaft; and a retaining device engaged by the threaded end of the fastening means; the head of the fastenin means and the retaining device lying in the opposite ends of the passage, respectively, and effective to clamp the shaft between them at diametrically opposite points, and to serve as a key to transmit rotary motion from the shaft to the element.

2. The combination with a rotary shaft, and an element having an axial bore to accommodate the shaft for rotation thereby; of means to key the element to the shaft, comprising a headed fastening means,- said element having an unthreaded passage formed diametrically therethrough and intersecting the axial bore; said shaft having a hole of less diameter than the passage and extending diametrically through the shaft and with which the passage is aligned, the fastening means lying in the unthreaded passage in said element and in the hole through the shaft; a tubular, non-rotatable member in one end of the passage, said member seating on the periphery of the shaft surrounding the diametrically extending hole in the shaft, and through which member a portion of the fastening means extends, the head of the fastening means being engageable with the outer end of the non-rotatable member, and a retaining device for the fastening means in the opposite end of the passage,

and engageable by: the fastening means to clamp the A shaft between the non-rotatable member and theretaining'devicei" 1 *3. In aldevice f'or keying together a rotariz shaft and an: element: to be rotated thereby, said element havingan axial 'bore to accommodate the shaft; of akeying device comprising a head'e'd fastenihgmeans saidshaft having a'hole formed diametrically therethrough; said element having an unthreaded p-assag'e'extending diametrically therethrough 1 and intersecting the bore of said element, said passage being of larger diameter than the hole threugh the shaft with which "it is aligned; the shank of 1 the 1' headed fastening mes-namin threaded and or -length capable of passing-through the r-hole in the shaft, with its head in one section "of :the passage and threade'd end in the opposite-section of thep a's= sage? a retainin g ma nssea'ted in said opposite section of the "Dassage' and engageable *by the threaded end of "thefasteningmeans, and a cupped spring: washer interposed between the head of the fastening means-and the shaft, 1 said washer having a central aperture through which the shank of the fasteningmeans passes, and expansibile as the fastening means tightehs on the shaft, toltake:u'pathexclearance ibetween the fastening means and the wall ofthe passage. (1

4. The combination with alrotary shaft, andan' element having-anaxialbore to. accommodate. the shaft forrotation :thereby; of means .to key :the element to the-shaft, comprising a headed fase tening means, having a threaded shank; said element having a passage extending therethrough intersecting the axial ,bore; said shaft having a hole therethrough ofgless diameter than the pas:- sage, aligned with, the passage, the ,headed fastening meanssfitting the hole in thev shaft with its head, projecting into one section of the passage and its threaded end projecting into the opposite section of the passage; a retaining means in said last-named section cooperable with and engaged by the threaded end of the fastening means to be drawn against the surface of the shaft; a centrally apertured spacing means interposed between the head of the fastening means and the shaft; and a resilient member located in one of the sections as the fastening means tightens, to take up clearance between the fastening means and the wall of the passage.

5. In a device to key a sprocket to a rotary shaft, the sprocket having a bore to accommodate the shaft; the combination of a headed screw; the shaft having a hole extending diametrically thereof; the sprocket having a diametrically extending unthreaded passage intersecting the bore of the sprocket, and of larger diameter than the hole through the shaft with which hole the passage is aligned; the screw being insertable through one end of the passage into the hole of the shaft, with the threaded end of the shank of the screw projecting into the opposite end of the passage, a retaining means fitting in said opposite end of the passage for engagement by the threaded end of the screw; and a spacing collar fitting the passage and having an aperture of similar diameter to that of the transverse hole through the shaft, and aligned therewith, the screw passing through the collar aperture with its head in contact with the outer end of the collar.

6. In a. device to key a sprocket to a rotary shaft, the sprocket having a bore to accommodate the shaft; the combination of a headed of the passage and expansible screw; the shaft having a hole extending dia-. metrically thereof, the sprocket having a dia metrically extending unthreaded passage intersecting the bore of the sprocket, and of larger diameter than the hole through the shaft with which the passage is aligned; a collar substantially fitting the passage and having an aperture therethrough of a diameter approximately of the diameter of the transverse hole through the shaft; the screw insertible in one end of the passage and through the centra1 aperture in the collar so that, when so inserted the threaded end of the shank of the screw projects into the opposite end of the passage, the head of the screw resting on the collar; a. retaining means insertible in and substantially fitting said opposite end of the passage for engagement by the threaded 7 end of the screw to draw the retaining means toward the shaft at a point diametrically opposite the head of the screw; and an expansible means seated in the passage and having a cen-- tral aperture through which the shank of the screw passes, said expansible means being compressible by the screw to take up the clearance between the screw and the wall of the passage.

'7. A keying device to transmit rotary motion from a shaft to a sprocket and to retain the sprocket on the shaft, comprising a, shaft having a hole formed transversely therethrough; a sprocket having a bore extending alongit axis of vrotation to slidingly accommodate the shaft,

and having a passage extending transverselyv through the sprocket of greater diameter than the diameter of the transverse hole through the shaft with which it is aligned; a screw passing through the transverse hole in the shaft, the head of the screw extending into one section of the passage on one side of the shaft, the threaded end of the screw extending into that section of the passage on the opposite side of the shaft;

a threaded retaining means slidingly fitted into the last-named section of the passage for engagement by the threaded end of the screw; and expansion means in the passage and through which means the screw passes, for expansion as the screw is tightened, to take up clearance between the screw and the wall of the passage.

8. The combination of a rotary shaft having a bore formed transversely therethrough; a filmsprocket having an axial bore in which the-shaft fits, said sprocket having a locking passage formed therethrough normal to said axial bore, said passage being of substantially greater di-. ameter than, and alignable with, saidtransverse bore through the rotary shaft; a thimble disposed snugly within one end of said locking passage and having a concave surface fitting congruently with a portion of said shaft adjacent said passage; locking means, engaging said. shaft snugly within said passage at the end thereof opposite to that engaged by said thimble; and a threaded element entered in the locking passage and the axial bore; said threaded element passing slidably through the thimble and threadably engaging through the locking means for drawing said locking means and thimble tightly into contact with said shaft.

HENRY F. HEIDEGGER. WILLY BORBERG.

REFERENCES CITED The following references are of record in th file of this patent:

1,921,866 Dina Aug. 8, 1933 

